There are certain types of amplifiers known in the art that include harmonic processing circuits provided for respective transistors to process harmonics present in the signals output from the transistors and a matching circuit situated at the stage following the harmonic processing circuits to combine the output signals of the transistors. In such an amplifier, the output terminals of transistors may be connected to each other through resistors in order to reduce oscillation that may occur due to phase differences between the output signals of transistors (see Patent Document 1, for example).
The point at which a harmonic processing circuit is coupled to a respective transistor may correspond to the antinode of a standing wave. In such a case, phase differences between standing waves occurring at the respective points may cause large electric power exceeding a tolerance level to be applied to the oscillation-suppression resistors connecting these points, thereby creating a risk of an open-circuit failure at the resistors.